Soft dome tweeters for dummies

There are some vexing problems with soft dome tweeters and I’ve been involved in one that was hard to believe. I’ll get to that in a moment but first; what’s a soft-dome tweeter?

Tweeters are the smallest drivers in the speaker and handle the high range sound. Soft dome tweeters have a dome about half the diameter of a golf ball and it’s soft. Very soft. Obviously too soft for the inquisitive among us – read children. Most speaker makers cover them with grilles to protect them from damage, a good idea because they damage easily.

The most common problem with soft-dome tweeters is that someone, maybe a kid or a furniture removal guy, presses them and leaves a big dint. It takes very little pressure to do this and yes, it doesn’t sound the same once dinted.

There are some creative ways people address this and most of them are incorrect. Lots of people figure they’ll bring the dint out with suction and grab the vacuum cleaner, but the average vacuum cleaner is way too powerful for this job and folk who do this wind up without any dome at all – it’s in the dust bag somewhere. Similarly do not prick the dome with a pin and then use the pin to pull it back into shape, you’re doing more damage. You can take it back to the dealer but he may have as much knowledge of fixing it as you, which is none at all.

A guy at a speaker factory once showed me his fix and it was simple. He put on latex gloves and applied gentle, v-e-r-y gentle pressure to the ridges at the ends of the dint. There can be three or four of these and he put a finger on each one and pushed very gently towards centre, and out it came. But this guy had done it lots of times. I am yet to build up the courage to do it once.

The lesson: Don’t touch soft dome tweeters.

The problem I had never struck before arose when a pathologist mate of mine bought new speakers and they sounded so bad he figured he may have made some sort of mistake hooking them up. So he called me.

The top end had an edge that grated like old tin cans dragged across a concrete floor. It was all over the place; harsh, serrated, abrasive and extremely uncomfortable to listen to. Yet these were good speakers, brand new and straight out of the box, three grand a pair. Something was wrong.

I checked his tone settings, I checked his connections, I checked his cables. Then I took the dust covers off to look at the drivers. And my highly qualified medical practitioner mate who knows as much about speakers as I know about pathology hadn’t taken the plastic protective covers off the soft-dome tweeters. The covers, hard plastic triangles covering the entire tweeter, protect the fragile domes during packing, unpacking and transit. Now they were blocking the high range sound, vibrating and bouncing sound every which way.

These covers are commonly orange and have a big exclamation point on them. This is supposed to make their removal obvious, but if you miss this message the instructions also tell you to remove them. My mate figured that he didn’t need instructions for speakers, just connect the cables and there you are.

I took them off, replaced the dust covers and his $3000 speakers sounded like $3000 speakers. He thinks I’m a genius. It’s nice. Please don’t tell him otherwise.